@Borromini Alright, and thanks for the heads up about tagging. I'm not sure what to make of that kernel tree, but the brcmfmac4366c-pcie.bin file on there is ~10x the size of the one provided in the guide. I tried putting that large brcmfmac4366c-pcie.bin on my router in /lib/firmware/brcm, but then I had to boot in failsafe mode and reset the router back to defaults.
@slh Ok! I can't find such a txt-file anyway and there's nothing mentioned about needing a .txt-file in the guides or previous posts..
So, I'm still looking for a solution.